To help protect the front element of my Olympus M.Zuiko 17mm lens,I like the $7.29 Rainbowimaging 37mm Vented Metal Hood Shadethat screws into the front threads. The vented hood is extremely light, which is important as to not stress the autofocusing mechanism of the 17mm prime.
I did a vignette test with the Rainbowimaging lens hood on the 17mm just to make sure they were compatible. It looks pretty good. Just a smidge in the corners. But you decide for yourself.
Personally, I like the way the Rainbowimaging lens shade looks on the 17mm, especially on my PEN mini. It's a good value and well made.
Take a look at the Olympus Micro Four Thirds Gear Guide for an overview of cameras, lenses, and accessories.